1. Technical Field
Exemplary aspects of the present invention relate to a liquid discharge head and an image forming apparatus including the liquid discharge head.
2. Related Art
An inkjet recording apparatus used as an image forming apparatus such as a printer, a facsimile machine, a copier, and a plotter includes an inkjet head serving as a liquid discharge head. The inkjet head includes nozzles, ink channels (hereinafter, also referred to as pressure liquid chambers) communicating with the nozzles, and pressure converters. The nozzles discharge ink droplets, and the pressure converters change pressure inside the ink channels to compress the ink.
For example, a piezoelectric pressure transducer is known as the pressure converter. The piezoelectric pressure transducer includes an electromechanical conversion element such as a piezoelectric element to generate pressure to be applied to ink inside a pressure liquid chamber that includes a wall formed of an elastically deformable wall member (a diaphragm). The piezoelectric element enables the wall member to be deformed by displacement of a drive unit. Such deformation of the wall member changes volume and therefore also pressure inside the pressure liquid chamber, thereby discharging ink droplets.
In addition to the piezoelectric element, a thermal actuator, a shape-memory alloy actuator, and an electrostatic actuator are known as pressure converters. The thermal actuator utilizes a phase change caused by film boiling of liquid by using an electrothermal conversion element such as a heat resistor. The shape-memory alloy actuator utilizes a metallic phase change caused by changes in temperature, whereas the electrostatic actuator utilizes electrostatic force.
In a case where droplets are discharged from the inkjet head, the pressure to be applied to the pressure liquid chamber needs to be increased. The pressure is generated to discharge the ink droplets. At the same time, the pressure is transmitted to a common liquid chamber used to supply ink. When this pressure is transmitted to the pressure liquid chamber again, pressure of the pressure liquid chamber fluctuates.
Particularly, in a case where an inkjet head with multiple nozzles for discharging ink is operated in a multichannel mariner, pressure fluctuation is large. The pressure fluctuation may cause resonance (mutual interference) of the pressure liquid chamber. Moreover, a resonance frequency of the vibration may match a drive frequency used during printing. If these frequencies match each other, the discharge of ink droplets is affected. This degrades image quality.
Accordingly, a pressure attenuation efficiency in the common liquid chamber needs to be enhanced to prevent such a situation, usually accomplished by increasing a volume of the common liquid chamber. Moreover, a damper (a pressure absorber) is provided between the pressure liquid chamber and the common liquid chamber to absorb pressure fluctuations inside the pressure liquid chamber.
For example, a liquid discharge head is capable of performing high-grade recording at high speed by efficiently attenuating pressure fluctuations while reducing resonance of a common liquid chamber. The liquid discharge head includes the common liquid chamber to supply liquid to a plurality of liquid chambers communicating with a plurality of respective nozzles. In a case where the liquid chambers are arranged in an X-direction, at least one wall of the common liquid chamber is provided in the X-direction and serves as a pressure-absorbing surface having lower rigidity than the other walls. In a case where a member that forms the pressure absorbing surface is divided into three portions in the X-direction, an average thickness of a center portion among the three portions is greater than that of each of both end portions.